Probe for detection of the concentration of various elements in molten metal

Abstract

A system is provided for measuring the concentration of an element in molten metal such as silicon, chromium, manganese or aluminum. The system includes a probe with a sensor having a solid electrolyte, a reference electrode in contact with a first surface of the electrolyte and an auxiliary electrode at a second surface thereof. The auxiliary electrode includes an oxide of the element to be measured and a metal-silicate selected from the group consisting of alkali metal-silicates, alkaline earth metal-silicates and mixtures thereof. The metal-silicate has a working point at about the temperature of the molten metal so as to form a viscous semi-molten mass adjacent the second surface of the electrolyte. The metal-silicate is capable of diffusing oxygen in the semi-molten state. Preferably the metal-silicate is in the form of a fibrous material so that it can be easily applied to the surface of the electrolyte.

We claim: 
     
       1. A sensor for use in a system for obtaining consistent in-situ electro-chemical measurements of the concentration of an element dissolved in molten iron-base metal, said sensor comprising: a solid electrolyte capable of conducting oxygen ions, a reference electrode in contact with a first surface of the electrolyte for providing a constant oxygen potential at a particular temperature, and an auxiliary electrode at a second surface of the electrolyte comprising an oxide of the element to be measured and a metal-silicate material selected from the group consisting of alkali aluminosilicate, alkaline aluminosilicate, alkali borosilicate, alkaline borosilicate and mixtures thereof, said metal-silicate material having a working point so as to form a viscous semi-molten mass on said second surface of the electrolyte at the temperature of measurement, said metal-silicate also being capable of diffusing oxygen in the semi-molten state.   
     
     
       2. The sensor of claim 1 wherein said metal-silicate comprises a fibrous material. 
     
     
       3. The sensor of claim 2 wherein the fibers of said fibrous metal-silicate material are comprised of said metal-silicate and the oxide of the element to be measured. 
     
     
       4. The sensor of claim 2 wherein the oxide of the element to be measured is physically mixed into the fibers of the fibrous metal-silicate material. 
     
     
       5. The sensor of claim 1 wherein the element to be measured is selected from the group consisting of silicon, chromium, manganese and aluminum and the oxide in said auxiliary electrode comprises SiO 2 , Cr 2  O 3 , MnO or Al 2  O 3 , respectively. 
     
     
       6. A probe element for use in a system for obtaining consistent in-situ electro-chemical measurements of the concentration of an element dissolved in molten iron-base metal, said probe element comprising: an elongated hollow cylindrical member,   a housing mounted in one end of the elongated hollow cylindrical member,   a metallic electrode, a thermocouple and a sensor mounted at spaced locations in said housing and protruding therefrom outwardly of said elongated hollow cylindrical member;   a protective cap enveloping the sensor, the metallic electrode and the thermocouple, for protecting them upon their immersion in the molten metal, said cap being composed of a consumable material which dissolves immediately after the immersion in the molten metal without substantially changing the composition of the molten metal so that said sensor, metallic electrode and thermocouple may be exposed to the molten metal;   said sensor including a solid electrolyte capable of conducting oxygen ions, a reference electrode in contact with a first surface of the electrolyte for providing a constant oxygen potential at a particular temperature, and an auxiliary electrode at a second surface of the electrolyte comprising an oxide of the element to be measured and a metal-silicate material selected from the group consisting of alkali aluminosilicate, alkaline aluminosilicate, alkali borosilicate, alkaline borosilicate, and mixtures thereof, said metal-silicate material having a working point so as to form a viscous semi-molten mass on said second surface of the electrolyte at the temperature of measurement, said metal-silicate also being capable of diffusing oxygen in the semi-molten state,   a plurality of electrical contacts adjacent an opposite end of the elongated cylindrical member, and   electrical conductors extending from said thermocouple, the reference electrode and said metal electrode respectively to said electrical contacts, said electrical contacts being adapted for contact with electrical contacts of a second probe element of said system.   
     
     
       7. The probe element of claim 6 wherein said metal-silicate comprises a fibrous material. 
     
     
       8. The probe element of claim 7 wherein the fibers of said fibrous metal-silicate material are comprised of said metal-silicate and the oxide of the element to be measured. 
     
     
       9. The probe element of claim 7 wherein the oxide of the element to be measured is physically mixed into the fibers of the fibrous metal-silicate material. 
     
     
       10. The probe element of claim 6 wherein the element to be measured is selected from the group consisting of silicon, chromium, manganese and aluminum and the oxide in said auxiliary electrode comprises SiO 2 , Cr 2  O 3 , MnO or Al 2  O 3 , respectively. 
     
     
       11. A system for obtaining consistent in-situ electro-chemical measurements of the concentration of an element dissolved in molten iron-base metal, said system comprising: first and second hollow elongated cylindrical probe elements which fit together end-to-end in socket and plug relation,   said first probe element including a housing mounted in one end thereof,   a metallic electrode, a thermocouple and a sensor mounted at spaced locations in said housing and protruding therefrom outwardly of said elongated hollow cylindrical member;   a protective cap enveloping the sensor, the metallic electrode and the thermocouple, for protecting them upon their immersion in the molten metal, said cap being composed of a consumable material which dissolves immediately after the immersion in the molten metal without substantially changing the composition of the molten metal so that said sensor, metallic electrode and thermocouple may be exposed to the molten metal;   and sensor including a solid electrolyte capable of conducting oxygen ions, a reference electrode in contact with a first surface of the electrolyte for providing a constant oxygen potential at a particular temperature, and an auxiliary electrode at a second surface of the electrolyte comprising an oxide of the element to be measured and a metal-silicate material selected from the group consisting of alkali aluminosilicate, alkaline aluminosilicate, alkali borosilicate, alkaline borosilicate, and mixtures thereof, said metal-silicate material having a working point so as to form a viscous semi-molten mass on said second surface of the electrolyte at the temperature of measurement, said metal-silicate also being capable of diffusing oxygen in the semi-molten state,   a plurality of electrical contacts adjacent an opposite end of said first probe element,   electrical conductors extending from said thermocouple, the reference electrode and said metal electrode respectively to said electrical contacts,   the second probe element including electrical contacts adjacent one end thereof for contact with the electrical contacts of the first probe element and electrical conductors extending from said contacts, and   an electrical circuit connected to said electrical conductors including a potentiometer for determining a potential difference between said reference electrode and the metal electrode exposed to the molten metal and a thermoelectric thermometer connected to said thermocouple for determining the temperature of the molten metal.   
     
     
       12. The system of claim 11 wherein said metal-silicate comprises a fibrous material. 
     
     
       13. The system of claim 12 wherein the fibers of said fibrous metal-silicate material are comprised of said metal-silicate and the oxide of the element to be measured. 
     
     
       14. The system of claim 12 wherein the oxide of the element to be measured is physically mixed into the fibers of the fibrous metal-silicate material. 
     
     
       15. The system of claim 11 wherein the element to be measured is selected from the group consisting of silicon, chromium, manganese and aluminum and the oxide in said auxiliary electrode comprises SiO 2 , Cr 2  O 3 , MnO or Al 2  O 3 , respectively. 
     
     
       16. A system for obtaining consistent in-situ electrochemical measurements of the concentration of an element dissolved in molten iron-base metal, said system comprising: an elongated hollow cylindrical probe element including a housing mounted in one end thereof,   a metallic electrode, a thermocouple and a sensor mounted at spaced locations in said housing and protruding therefrom outwardly of said probe;   a protective cap enveloping the sensor, the metallic electrode and the thermocouple, for protecting them upon their immersion in the molten metal, said cap being composed of a consumable material which dissolves immediately after the immersion in the molten metal without substantially changing the composition of the molten metal so that said sensor, metallic electrode and thermocouple may be exposed to the molten metal;   said sensor including a solid electrolyte capable of conducting oxygen ions, a reference electrode in contact with a first surface of the electrolyte for providing a constant oxygen potential at a particular temperature, and an auxiliary electrode at a second surface of the electrolyte comprising an oxide of the element to be measured and a metal-silicate material selected from the group consisting of alkali aluminosilicate, alkaline aluminosilicate, alkali borosilicate, alkaline borosilicate, and mixtures thereof, said metal-silicate material having a working point so as to form a viscous semi-molten mass on said second surface of the electrolyte at the temperature of measurement, said metal-silicate also being capable of diffusing oxygen in the semi-molten state, and   electrical circuit means for determining the potential difference between said reference electrode and the metal electrode exposed to the molten metal and for determining the temperature of the molten metal.